Many bacteria have a sophisticated mechanism for metabolic regulation that involves microcompartments. These bacterial microcompartments are made up of unique protein shells similar in structure to a viral capsid and enclose two or more enzymes in a particular reaction pathway. Carboxysomes from cyanobacteria and chemoauxotrophs are the most well known bacterial microcompartments. Within the last few years, the crystal structures of several shell components have been solved and have led to remarkable progress in the knowledge of subunit assembly and function of individual components. So far, there has been no report of heterologous assemblies of bacterial microcompartments in eukaryotic organisms. This project will target multiple carboxysome proteins into chloroplasts. This study will employ transient expression of foreign proteins fused with fluorescent tags by agroinfiltration technique. Any molecular complex assembled from the expressed proteins will be monitored with confocal microscopy, and the structures formed will be characterized by electron microscopy. In addition, this work will generate stable transgenic lines, in which carboxysome proteins are expressed from either the nucleus or the chloroplast genome. By expressing all necessary carboxysome structural components, this project will attempt to assemble the carboxysome microcompartment shells in eukaryotes. In addition, this study will determine whether it is possible to target foreign proteins to the carboxysome shells. The proposed study is an important step for engineering novel microcompartments and will have potential future applications in areas such as drug delivery, metabolic engineering and biotechnology.